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A marked increase in drilling for coalbed gas has occurred
in southeastern Kansas in the last three years, with a commensurate increase
in coalbed gas production.
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Most of the activity for coalbed gas has been in southeastern
Kansas in the Cherokee basin, but isolated projects farther north in the
Bourbon arch and Forest City basin are in progress.
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Most Kansas coals are thin (<2 ft [0.6 m] thick),
but several can be encountered in a given well. Water pumped from the
coals is easily disposed, usually into the Arbuckle Dolomite, which lies
a few hundred feet below the deepest coals.
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The Forest City basin has several coal seams that are
likely older than the Riverton coal, which is generally the oldest coal
in the Cherokee basin and Bourbon arch.
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Thickness trends in many coals follow a NNE-SSW depositional
strike.
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Thermal maturation increases southward into the Cherokee
basin. This increase in maturation is manifest in the greater heating
values of conventional gas and coalbed gas in this region.
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A mixed biogenic and thermogenic origin of the coalbed
gas in eastern Kansas is indicated by gas chemistry and stable isotopes.
Some of the biogenic gas may be due to biogenic oxidation of existing
hydrocarbons.
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Possible biogenic and thermogenic production fairways
may be present in eastern Kansas.